Combined centrolinead and parallel-rule.



No. 644,|84. Patented Feb. 27, I900. G. McMULLEN.

COMBINED CENTROLINEAD AND PARALLEL RULE.

(Application filed June 16, 1899.)

(No Model.)

I W- z NITED STATES PATENT rrrc.

COMBINED CENTROLINEAD AND PARALLEL-RULE.

SPECIFICATION forming part of Letters Fatent No. 644,184, datedFebruary27, 1900. Application filed June 16, 1899. Serial No. 720,792. (Nomodel.)

To all whom it may concern:

Be it known that I, GEORGE MOMULLEN, a subject of the Queen of GreatBritain and Ireland, residing at Perth,inthe' Colony of WesternAustralia, have invented an Improved Instrument for Use in PreparingPerspective or other Drawings, (in respect whereof I have applied for apatent in Great Britain to bear date February 4,1899, No. 2,578, and inGermany on February 11, 1899, No. M. 16,395,) of which the following isa specification.

This invention relates to improved means for use in preparingperspective and geomet rical drawings, its object being to provide aninstrument whereby centrolineads may be produced with sufficientaccuracy for the purpose of perspective drawing and which may be readilyadapted for use in drawing parallel lines. Centrolineads are open toobjection, as they are not easily or conveniently adapted for thepurpose intended and are not capable of being readily adjusted forpreparing drawings in perspective on a large or small scale. Theseobjections are obviated in the improved apparatus hereinafter described.Theinstrument may be constructed of metal or other suitable material.

In the accompanying drawings, Figure 1 is a plan of the instrumentcomplete. Fig. 2 is an elevation. Figs. 3 and 4 are transverse sectionstaken, respectively, on the lines 00 m and y y, Fig. 1. Fig. 5 is atransverse section taken on the line a 2, Fig. 1.

The blade A has its outer or working edge beveled or chamfered and isconnected to the blade B by means of slotted links 0 and D, whereof theextremities work on pivots c d c d. The pivots c and at are carried bytongued slides ct b, which Work in slots adapted for their receptionformed in the blades A and B. The respective pivots c and d are fixturesin the blades A and B. The links 0 and D, besides being arranged topivot at their extremities, are also furnished with an adjustable pivotE, carried by the tongued slide F, the latter working in the groovedslot in the link D. The pivot E passes through another tongued slide F,which is capable of being moved along the grooved slot in the link 0 bymeans of the screw G, the latter being furnished with a milledturning-nut G.

The tongued slide F passes freely along the screw H and may be securedin position thereon by the nuts H H. For determining the radius of anycircle desired and the angle of any perspective required the link 0 ismarked with the respective distances of the center of the circle from apoint in the center of the blade A, and when the pivot E is broughtopposite this figured distance and the blade B held stationaryconverging or approximately converging lines may be produced along theblade A. Thus perspective or convergent lines may be drawn withapproximate accuracy, such lines apparently converging to a long andinaccessible vanishing point. As an illustration, if the link is set atnine feet and the pivot is fixed there the lines which are drawn alongthe blade A will converge approximately to the center of a circle havinga radius of nine feet, and so with any other measurements to which thepivot may be fixed. When the pivot E is fixed in the center of the linkC, as shown, the lines drawn along the blade A willbe parallel. Theimproved centrolinead can thus be readily adjusted to serve as aparallel-rule, such rule being capable of doing the workstraightforwardly instead of in the manner achieved by parallel-rules ofthe usual construction. This will be found a great advantage. Theinstrument may also be used for doing the work of an ordinary T-square.

I is a fixing-piece whereby the instrument may be secured to adrawing-board or other surface, the bladeB being hinged to the saidfixing-piece at K. I I are screws for adjusting the angle of inclinationof the blade B. All the pivots are provided with nuts.

What I claim as my invention, and desire to secure by Letters Patent,is-

1. An instrument for use in preparing perspective and other drawingscomprising a pair of blades connected by crossed links each attached atone end by a fixed pivot and at the other end by a sliding pivot to therespective blades and slotted for the greater portion of its length forthe reception of a slide and adjustable pivot whereby the instrument isrendered available for drawing either radial or parallel lines; one ofthe blades being provided with a working edge and the other with meansfor attaching the instrument to a drawing-board, substantially as hereindescribed. v

2. In an instrument for use in preparing 5 perspective and otherdrawings the combination with a pair of blades connected bydiagonally-pivoted slotted plates, whereof one is provided with thegraduated scale C, of the tongued slides F F and screws G and H, sub- 10stantially as and for the purpose specified.

In an instrument for use in preparing perspective drawing and fordrawing parallel lines, the combination, with the blades A, B, of theslotted links 0, D, the pivots c, c, d, d, 15 the tongued slides a, b,the adjustable pivot

